状态模式

UML图

代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace YJY
{
class Account
{
public AccountState State { get; set; }
public string Owner { get; set; }
public double Balance { get; set; }

public Account(string owner, double initialAmount)
{
Owner = owner;
Balance = initialAmount;
State = new 访客(this);
}

public void SetBalance(double amount)
{
Balance = amount;
}

public void Deposit(double amount)
{
Console.WriteLine("存款 {0}.", amount);
State.Deposit(amount);
Console.WriteLine("客户状态变更为 {0}", State);
}

public void Consume(double amount)
{
Console.WriteLine("消费 {0}.", amount);
State.Consume(amount);
Console.WriteLine("客户状态变更为 {0}", State);
}
}
abstract class AccountState
{
protected Account Account;
public abstract void Deposit(double amount);
public abstract void Consume(double amount);
public abstract void Check();
}
class 访客 : AccountState
{
public 访客(Account account)
{
Account = account;
}

public override void Deposit(double amount)
{
Account.Balance += amount;
Console.WriteLine("向" + Account.Owner + "账户中存入" + amount + "，账户余额为" + Account.Balance);
Check();
}

public override void Consume(double amount)
{
double newBalance = Account.Balance - amount;
Account.Balance -= amount;
Console.WriteLine("在" + Account.Owner + "账户中消费" + amount + "，账户余额为" + Account.Balance);
Check();
}
public override void Check()
{
if (Account.Balance > 100 && Account.Balance < 1000)
{
Account.State = new 会员(Account);
}
else if (Account.Balance >= 1000)
{
Account.State = new 贵宾(Account);
}
}
}
class 会员 : AccountState
{
public 会员(Account account)
{
Account = account;
}

public override void Deposit(double amount)
{
Account.Balance += amount;
Console.WriteLine("向" + Account.Owner + "账户中存入" + amount + "，账户余额为" + Account.Balance);
Check();
}

public override void Consume(double amount)
{
double newBalance = Account.Balance - amount;
Account.Balance -= amount;
Console.WriteLine("在" + Account.Owner + "账户中消费" + amount + "，账户余额为" + Account.Balance);
Check();
}
public override void Check()
{
if (Account.Balance > 0 && Account.Balance <= 100)
{
Account.State = new 访客(Account);
}
else if (Account.Balance >= 1000)
{
Account.State = new 贵宾(Account);
}
}
}
class 贵宾 : AccountState
{
public 贵宾(Account account)
{
Account = account;
}

public override void Deposit(double amount)
{
Account.Balance += amount;
Console.WriteLine("向"+Account.Owner+"账户中存入"+amount+"，账户余额为"+Account.Balance);
Check();
}

public override void Consume(double amount)
{
double newBalance = Account.Balance - amount;
Account.Balance -= amount;
Console.WriteLine("在" + Account.Owner + "账户中消费" + amount + "，账户余额为" + Account.Balance);
Check();
}
public override void Check()
{
if (Account.Balance > 100 && Account.Balance < 1000)
{
Account.State = new 会员(Account);
}
else if (Account.Balance > 0 && Account.Balance <= 100)
{
Account.State = new 访客(Account);
}
}
}
class Program
{
static void Main(string[] args)
{
Account account = new Account("YJY", 0);
Console.WriteLine("用户名:"+account.Owner);
Console.WriteLine("初始金额:"+account.Balance);
Console.WriteLine("------------------");
account.Deposit(50);
Console.WriteLine("-------------------");
account.Deposit(200);
Console.WriteLine("-----------------------------------------");
account.Deposit(800);
Console.WriteLine("-----------------------------------------");
account.Consume(100);
Console.WriteLine("---------------------");
account.Consume(900);
Console.WriteLine("-----------------------------------------");
}
}
}

运行结果

状态模式

原文：http://www.cnblogs.com/Yang-jy/p/5093583.html